Question

I have a situation where i need to start two threads one after the other. I tried the following code snippet, here i could able to start the Thread12 but not able to start Thread2. How can i start both….?
How to start 2 threads one ofter the other…?

Code snippet

class Thread1(QtCore.QThread):

    Thread1Signal = QtCore.pyqtSignal(str)

    def __init__(self):
        super(Thread1, self).__init__()

    def run(self):
        print 'Thread1 started'
        While True:

            #some statments
            if Condition:
                Thread1Signal.emit('Yes')
            else:
                Thread1Signal.emit('No')

class Thread2(QtCore.QThread):

    Thread2Signal = QtCore.pyqtSignal(str)

    def __init__(self):
        super(Thread2, self).__init__()

    def run(self):
        print 'Thread2 started'
        While True:

            #some statments
            if Condition:
                Thread2Signal.emit('Yes')
            else:
                Thread2Signal.emit('No')

class MainClass(QtCore.QObject):

    MainSignal1 = QtCore.pyqtSignal(str)
    MainSignal2 = QtCore.pyqtSignal(str)

    def __init__(self):
        super(MainClass, self).__init__()   

        Threadinstance1 = Thread1()
        Threadinstance1.Thread1Signal.connect(MainSignal1)

        Threadinstance2 = Thread2()
        Threadinstance2.Thread2Signal.connect(MainSignal2)


   def start(self):

       Threadinstance1.start()
       Threadinstance2.start()                #Thread2 never starts.

def signal1called(s):

    print s


def signal2called(s):

    print s

if __name__=='__main__':
    app = AtGui.QApplication(sys.argv)
    temp = MainClass()
    temp.MainSignal1.connect(signal1called)
    temp.MainSignal2.connect(signal2called)
    temp.start()
    sys.exit(app.exec()_)

Answer 1

You will be using QRunnable and QThreadPool, something like this:

import sys

from PyQt4.QtGui import QApplication
from PyQt4.QtCore import QThreadPool, QObject, QRunnable, pyqtSignal

class WorkerSignals(QObject):
    result = pyqtSignal(int)

class Worker(QRunnable):
    def __init__(self, task):
        super(Worker, self).__init__()

        self.task = task
        self.signals = WorkerSignals()

    def run(self):
        print 'Sending', self.task
        self.signals.result.emit(self.task)

class Tasks(QObject):
    def __init__(self):
        super(Tasks, self).__init__()

        self.pool = QThreadPool()
        self.pool.setMaxThreadCount(1)

    def process_result(self, task):
        print 'Receiving', task

    def start(self):
        for task in range(10):
            worker = Worker(task)
            worker.signals.result.connect(self.process_result)

            self.pool.start(worker)

        self.pool.waitForDone()

if __name__ == "__main__":
    import  sys

    app = QApplication(sys.argv)
    main = Tasks()
    main.start()
    sys.exit(app.exec_())